The present invention relates to a data input terminal device such as a pointing device that is a peripheral device for a host computer and that outputs input operation data to the host computer. More specifically, the present invention relates to a data input terminal device that can be connected to a host computer using two types of communication interfaces: a UART interface and a USB interface.
Conventionally, serial communication is generally used for data communication between a host computer such as a personal computer and a data input terminal device connected to the host computer as a peripheral. In serial communication, data is sent and received using communication cables and connectors that are compatible with RS-232C, which is a communication standard from the Electronic Industries Alliance (EIA) or Arlington, Va. According to the RS-232C communication standard, byte data output, for example, from a parallel bus of a central processing unit (CPU) must be converted to serial bit streams, and serial bit streams must be converted to parallel byte data handled by the CPU. A UART (Universal Asynchronous Receiver Transmitter) is often equipped in the host computer or the data input terminal device for this purpose.
However, in recent years, sending and receiving data between a host computer and a data input terminal device using other interfaces, such as a Universal Serial Bus (USB), as supported by the USB Implementers Forum, Inc. of Portland, Oreg., or by another interface compliant with a different serial communication standard (for example, the IEEE 1394 or FIREWIRE standard supported by the 1394 Trade Association of Southlake, Tex.) is becoming more prevalent. In USB communication, interrupt transfers are performed where the host computer receives input operation data from the data input terminal device at a fixed interval that does not inconvenience the operator. This makes it possible to allow data to be sent without interrupt handling on the host computer side, making it especially widely used for connecting a pointing device such as a mouse or joystick to a host computer.
As described above, the UART interface and the USB interface follow different standards. Network modules can be used to send and receive data using either communication interface by providing both a UART interface and a USB interface (see, e.g., Japanese Laid-Open Patent Publication Number 2005-333224, page 4, line 22, through page 5, line 29, and FIG. 1)
FIG. 3 is a simplified block diagram of a network module 100 based on a short-range wireless communication system known as BLUETOOTH, as supported by the BLUETOOTH Special Interest Group (SIG) of Bellevue, Wash. A BLUETOOTH IC chip 101 is mounted on a module substrate 102. Four external connection terminals 103A, 103B, 103C, 103D are provided at an end of the module substrate 102, which respectively serve as a UART RTS terminal, a UART CTS terminal, a UART IN terminal or a USB D+ terminal, and a UART OUT terminal or a USB D− terminal.
To allow data to be sent and received from either a UART interface or a USB interface, the BLUETOOTH IC chip 101 is equipped with a UART RTS terminal 104A, a UART CTS terminal 104B, a UART IN terminal 104C, a UART OUT terminal 104D, a USB D+ terminal 104E, and a USB D− terminal 104F.
As the figure shows, the RTS terminal 103A and the CTS terminal 103B at the end of the module substrate 102 are connected to the corresponding RTS terminal 104A and CTS terminal 104B, respectively, of the BLUETOOTH IC chip 101. Also, the external connection terminal 103C which serves as both a UART IN terminal and a USB D+ terminal is switchably connected to the IN terminal 104C and the D+ terminal 104E of the BLUETOOTH IC chip 101 by way of a jumper 105a of a double-pole double-throw jumper selection switch 105. The external connection terminal 103D which serves as both a UART OUT terminal and a USB D− terminal is switchably connected to the OUT terminal 104D or the D− terminal 104F of the BLUETOOTH IC chip 101 by way of a jumper 105b of the switch 105.
In this conventional network module 100, the jumpers 105a, 105b can be switched to the UART IN terminal 104C and the UART OUT terminal 104D to allow sending and receiving of data to an external device by way of the UART interface. The jumpers 105a, 105b can be switched to the USB D+ terminal 104E and the USB D− terminal 104F to allow sending and receiving of data by way of the USB interface.
However, a manually operated switch 105 is necessary to select between the UART interface and the USB interface, increasing the number of parts as well as requiring the inconvenience of manually switching the jumpers 105a, 105b. In particular, this selection operation is especially inconvenient when the switch 105 on the network module 100 is installed inside the device, as shown in the figure. Also, since the selected state is not visible, the communication interface may be switched erroneously.